What is a 3D laser scanner

A 3D laser scanner is a device that captures real-world objects or environments, effectively creating a 3Dimensional "point cloud" which is a spatially relevant copy of the real thing.   The collected data, or "point cloud" can then be used as is, or further refined into a meshed 3D surface or model useful for as-builting, surveying, or reverse engineering.

3D laser scanners are used extensively in a wide variety of applications including:
the ever popular "as-builting", architecture, heritage restoration, facility management, procecess/power/piping, construction, surveying, forensics, accident reconstruction, film/movies, and game development.Practically every industry can benefit from super accurate and high speed 3D reality data generation. 

Non-contact 3D laser scanners have weaknesses in regards to capturing data on shiny, or mirror surfaces.  Often black surfaces, especially glossy black, tend to cause problems as well.  These weaknesses are purely a function of optics, and they can be overcome easily, a thin powder can be applied to problematic surfaces which can later be blown off with no ill effect.

A 3D scanner is recommended to capture anything which needs to be an accurate, spatially relevant, 3D geometric surface or environment. The measured points, often numbering in the millions, form what is called a point cloud.  these points can then be used to extrapolate the shape of the subject or environment. If color information is collected at each point, then therefore each point retains its color properties which define the surface of the subject.

Similar to a camera, older 3D laser scanners had/have a cone-like field of view, they can only collect information that is not obscured due to line of sight or occlusions.  However newer laser scanners are capable of collecting entire environments in a single 360 field of view (FOV) - everything in sight is captured.  3D laser scanners collect distance information thousands of times a second, while a camera collects color information within its field of view.  The resultant data is a 3D "picture" produced by the 3D scanner, and it describes the distance to an object or surface at each point in the picture. 

Sometimes all you need from a high speed laser scanner is a single scan, but for most situations, a single scan will not produce a complete model of the subject so multiple scans, even hundreds, from many different locations, are required to obtain 3D data about all sides of the subject.  The scans must be brought together into a common reference system, this process is usually called alignment or registration.  The newly aligned or registered point clouds are then merged to create a complete model.

Generally speaking everything created by a 3D laser scanner is in a spherical coordinate system in which the scanner is the origin and the vector out from the front of the scanner is φ=0 and θ=0, then each point in the picture is associated with a φ and θ and the r component which is the distance from the origin (the laser scanner itself).  Spherical coordinates fully describe the three dimensional position of each point in the point cloud in a local coordinate system relative to the scanner however, the scanner typically internally translates the spherical coordinates into the cartesian system or rectangular coordinate system using x, y, z for length, width, and height.

Laser scanners are non contact measurement and imaging solutions of which there are two basic technologies, the older time-of-flight, and the cutting edge phase-shift laser scanners.